ST. LOUIS — Will Middlebrooks looked bewildered, flummoxed, aggravated. As would we all, had we just played a starring role in arguably the most bizarre game ending in World Series history.

We’ll need more time to determine whether another adjective — defined — will apply to the young Red Sox third baseman. For this is the sort of play, with the sort of impact, that certainly can define a player’s career. And this is the sort of concept to which Red Sox historians can relate all too well. Right, Bill Buckner?

“I don’t understand it,” Middlebrooks said, after the Cardinals recorded a walk-off, 5-4 victory in Game 3 of this Fall Classic as a result of Middlebrooks’ obstruction of Allen Craig. “I don’t understand it. I can’t do anything different there. I have to dive for that ball. I’m not in the baseline. … I don’t understand it.”

The Cardinals now lead this Series, two games to one, and the Red Sox must hope that their ailing Game 4 starting pitcher Clay Buchholz can summon the strength to compete — or that their lineup, missing one of its biggest weapons thanks to the absence of the designated hitter at Busch Stadium, pulverizes Cardinals starter Lance Lynn.

What the American League champions can’t do is launch any sort of legitimate protest. Every indication is that the umpiring crew got this right, no matter how blameless Middlebrooks was in the play.

“Obstruction is the act of a fielder obstructing a runner when not in the act of fielding the ball,” umpiring crew chief John Hirschbeck explained after the game. “It does not have to be intent.”

That ends that discussion. We might be replaying the sequence for a very long time: Cardinals have men on second and third with one out, and Jon Jay knocks a grounder to drawn-in Boston second baseman Dustin Pedroia, who throws the ball home for the easy tag of Yadier Molina. Craig, battling a left foot injury, was hobbling toward third base, and Red Sox catcher Jarrod Saltalamacchia threw to third in an attempt to complete an unorthodox, 4-2-5 double play.

Saltalamacchia threw wide to Middlebrooks’ left, however, and Middlebrooks dove to the ground to try to stop the ball. He laid down right in Craig’s path, and when he tried to get back up, he tripped Craig with his legs.

As Hirschbeck explained, it doesn’t matter whether that action was inadvertent or intentional. Once third-base umpire Jim Joyce signaled obstruction, all that mattered was letting the scenario play out. Since Craig was out at home on a bang-bang play (after Daniel Nava threw the ball back home to Saltalamacchia), the umpires ruled Craig would have scored if not for the obstruction.

“The rule is that the runner has every right to go to home plate at that particular play unobstructed without any liability,” Joyce said. “He doesn’t have to get out of the way, he just has the baseline. And unfortunately, the defensive player was there.”

This gets my nomination for the most bizarre play ever because it took everyone — on the field, in the stands, up in the press box, those at home — time to absorb exactly what had happened. As Major League Baseball noted, never before had a World Series game concluded on an obstruction call.

“It’s frustrating after we fight back against some of the best pitchers in the game,” Middlebrooks said, referring to Boston’s a eighth-inning rally off Cardinals closer Trevor Rosenthal. “It’s going to be a tough one to swallow. I feel like we needed to win that game. We’re really going to have to kick it into gear [Sunday].”

If they don’t, and if the Red Sox can’t climb back out of their current hole, Middlebrooks — who entered the game as a pinch hitter in the seventh inning — faces a future in which he might known be known best as the obstruction guy.

It would represent a cruel fate, an undesired way to be defined. It isn’t too late for him and his teammates to change that. To turn this crazy ending into a footnote to an otherwise magical season.